Process of setting the length of an upper steering arm

ABSTRACT

A process of setting the length of an upper steering arm of an attaching device of a tractor. The attaching device includes the upper steering arm with a power drive provided for length setting purposes; a length sensor to determine the actual length of the upper steering arm; two lower steering arms with a lifting mechanism to lift and lower the lower steering arm; a lift sensor to determine the actual position of lift of the steering unit; as well as a control unit. The nominal lengths of the upper steering arm ( 7 ), to be determined as a function of the directions of movement of the lifting mechanism, are stored in the control unit. Determining the actual length of the upper steering arm ( 7 ), the actual position of lift of the lifting mechanism and the direction of movement of the lifting mechanism. Comparing the actual length with the nominal length stored for the direction of movement and for the actual position of lift as determined, and actuating the power drive ( 27 ) for setting the length of the upper steering arm ( 7 ) to the nominal length if the actual length deviates from the nominal length.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No.10350651.9, filed Oct. 29, 2003, which application is herein expresslyincorporated by reference.

FIELD OF THE INVENTION

The invention relates to a process of setting the length of an uppersteering arm of an attaching device of a tractor. The attaching deviceincludes the upper steering arm with a power drive provided for lengthsetting purposes. A length sensor determines the actual length of theupper steering arm. Two lower steering arms, with a lifting mechanism,lift and lower the lower steering arms. A lift sensor determines theactual position of lift of the lifting mechanism. A control unit affectsthe operation.

BACKGROUND OF THE INVENTION

A prior art process of setting the length of an upper steering arm isshown in German Patent No. DE 197 47 949 C2. Here, the actual length ofthe upper steering arm is determined by a length sensor and the positionof lift of the lifting mechanism is determined by a lift sensor. Foreach lift position, a nominal length of the upper steering arm isstored. The actual length of the upper steering arm is compared with thenominal length. If the two values deviate, a power drive is actuatedwhich moves the upper steering arm to its nominal length. An attachedimplement is thus lowered and lifted with identical movement sequences.However, when used with soil working implements, this process can leadto non-optimum treatment of the soil.

Further processes for setting the length of an upper steering arm areshown in U.S. Pat. No. 5,188,502. This patent deals with setting thelength of two upper steering arms of a construction machine. With onedescribed process, one or several positions can be set automaticallyfrom any starting position. The movement from the starting position tothe stored end position is continuously calculated. Depending on thestarting position, different movement sequences can take place into theend position. Furthermore, the implement can be lifted and lowered inparallel without pivoting the implement.

SUMMARY OF THE INVENTION

In accordance with the invention, a tractor includes an attaching devicewhich comprises an upper steering arm with a power drive to providelength settings. A length sensor determines the actual length of theupper steering arm. Two lower steering arms include a lifting mechanismto lift and lower the lower steering arms. A lift sensor determines theactual position of lift of the lifting mechanism. The process of settingthe length of an upper steering arm of an attaching device of a controlunit links the parts together. A tractor comprises the steps ofproviding nominal lengths of the upper steering arm, the nominal lengthsare stored in the control unit as a function of positions of lift anddirections of movement of the lifting mechanism to be determined;determining the actual length of the upper steering arm; determining theactual position of lift of the lifting mechanism; determining thedirection of movement of the lifting mechanism; comparing the actuallength with the stored nominal length for the direction of movement tobe determined and for the actual position of lift to be determined; andcontrolling the power drive for setting the length of the upper steeringarm to the nominal length if the actual length deviates from the nominallength.

When using a plow for example, it is possible, when lifting the plow, toplace it into a steep position as late as possible. Further, whenlowering the plow, it is possible to lower the plow in a steep positionin order to improve its furrowing of the soil. Further, nominal lengthsfor the direction of movement of lifting the lifting mechanism for thepositions of lift to be determined are stored in a memory of the controlunit in the form of a first characteristic curve. Also, the nominallengths for the direction of movement of lowering the lifting mechanismfor the positions of lift to be determined are stored in the memory inthe form of a second characteristic curve. The first characteristiccurve deviates from the second characteristic curve.

Accordingly, the speed at which the upper steering arm is set, startingfrom a lowered position of the lifting mechanism, at least over part ofthe lifting path to a lifted position of the lifting mechanism, islimited during the lifting phase. This enables the maximum hydraulicconveying power for the lifting mechanism to be available. This is ofparticular interest in those cases where the maximum hydraulic conveyingpower of the hydraulic system is not designed to operate both the uppersteering arm and the lifting mechanisms at maximum power.

The upper steering arm can be manually set by an operative to achieve afloating position where the length of the upper steering arm can be setfreely. If a signal is relieved by the control unit from the operatingunit, the upper steering arm is freely movable with respect of itslength.

Furthermore, the setting of the floating position can be dependent uponthe position of lift. Accordingly, releasing information is provided tothe effect that a floating path is to be set at the upper steering armif the position of lift to be determined is within a certain storedrange of the position of lift. Furthermore, the actual position of liftof the lifting mechanism is determined whereupon the actual position oflift is compared with the range of positions of lift stored for thereleasing information. The upper steering arm is released so that theupper steering arm is freely movable with respect of its length if theactual position of lift is within the range of positions of lift storedfor the releasing information.

To delimit the floating path of the upper steering arm, the control unitis provided with nominal lower length limits and nominal upper lengthlimits as a function of the positions of lift of the lifting mechanismto be determined. The release of the upper steering arm and theactuation of the power drive take place so that the upper steering arm,with respect to its lengths, is freely movable between the nominal lowerlength limits and the nominal upper length limits. Thus, this ensuresthat the floating path is delimited by the hydraulic mechanism withoutthe need to provide mechanical stops.

A limit value is stored in the control unit to ensure that the floatingpath cannot be set when an implement is lifted. Such lifting wouldresult in the implement being articulated while the floating path isbeing set. This could cause damage to the attaching device and to theimplement. The limit value stored in the control unit represents themaximum force acting on the upper steering arm. At this maximum force,the upper steering arm can be released to achieve a floating path. Anactual value, which represents the force acting on the upper steeringarm, is determined and compared with the limit value. The upper steeringarm is released only if the actual value is lower than the limit value.When a hydraulic upper steering arm is used, it is possible to measure,as a representative value, the actual value of the hydraulic pressure ina cylinder of the upper steering arm. The pressure corresponds to aforce at the upper steering arm which loads the upper steering armtowards longer lengths. If the pressure, and thus the force at the uppersteering arm is too high, this means that the implement has been liftedand, during the release of the upper steering arm, would pivotdownwardly in an uncontrolled way.

The inventive process can be loaded in the form of a computer programinto the control unit and executed by the control unit. In addition, theprocess can be made available on a computer program product, such as aCD ROM.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a diagrammatic illustration view of a tractor with animplement attached to the attaching device of the tractor;

FIG. 2 is a flow diagram of the inventive process;

FIG. 3 is a flow diagram of the process stages for manually setting afloating position at the upper steering arm;

FIG. 4 is a flow diagram of the process stages for automatically settinga floating position at the upper steering arm;

FIG. 5 is a flow diagram of the process stages for setting a limitedfloating path; and

FIG. 6 is a flow diagram of the process stages for initializing thesystem prior to setting a floating position at the upper steering arm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

FIG. 1 shows a tractor 1 with an attached implement 2. The tractor 1 canbe driven on soil which can be worked by the implement 2. Two lowersteering arms 4, which are arranged side by side, are provided at therear of the tractor 1. The two lower steering arms are articulatablyconnected to the tractor 1 and at the upper end of each is secured witha coupling hook 5. FIG. 1 shows only one of the two lower steering arms4. The coupling hooks 5 of the lower steering arms 4 are connected tosuitable coupling mechanisms 6 of the implement 2. An upper steering arm7 is connected via a jointed connection 8 to the rear of the tractorabove the two lower steering arms 4. At its free end, the upper steeringarm 7 includes a coupling hook 9 which provides a connection with acoupling mechanism 10 of the implement 2.

The lower steering arms 4 are each connected by a lifting strut 12 to alifting arm 11. The lifting arms 11 are rotated by a driveshaft 14 tolift or lower the lower steering arms. The lifting arms 11 and thedriveshaft 14 form a lifting mechanism whose setting with respect toheight, is recorded by a lift sensor 13. The lift sensor 13 determinesthe rotational position of the driveshaft 14. The lift sensor 13 can beprovided on one or both of the lower steering arms 4 to measure theangular position of the lower steering arms 4 relative to the rear ofthe tractor. The upper steering arm 7 is associated with a length sensor15. The length sensor 15 determines the actual length of the uppersteering arm 7. The lift sensor 13 and the length sensor 15 areconnected to a control unit 16 in which the recorded data is furtherprocessed. Furthermore, a power drive is connected to the upper steeringarm 7. The power drive is likewise connected to the control unit 16.Thus, the upper steering arm 7 can be actuated by the control unit 16.An operating unit 44 is provided to effect manual setting of the controlunit 10. The operating unit 44 is connected to the control unit 16.

FIG. 2 shows a flow diagram of the process in accordance with theinvention. At process stage 17, the required data is stored and madeavailable. Nominal length value of the upper steering arms with respectto different positions of lift and both directions of movement of thelifting mechanism, lowering or lifting of the lifting mechanism, arestored in a memory 18 of the control unit. For example, it is possibleto provide two different characteristic curves 19, 20 for lifting orlowering the lifting mechanism. If, for example, when using a plow, theplow is to be lowered in a steep position in order to improve thecarving of the plow and if, during the lifting operation, it should bepossible for initially only the lifting mechanism to be operated, withthe upper steering arm 7 being shortened after the completion of thelifting operation in order to place the plow into a steep position, itis possible to store two different characteristic curves 19 and 20. Thesubsequent shortening of the upper steering arm 7, after the implementhas been lifted, is advantageous. This is due to, initially, the entirehydraulic power being available and can be used for lifting purposes.Only after completion of the lifting operation is the hydraulic powermade available to the upper steering arm 7, thus permitting quicklifting of the plow.

The actual length of the upper steering arm 7 is determined duringprocess stage 21. The actual position of lift of the lifting mechanismis measured by the lift sensor during process stage 22. The measureddata is passed onto the control unit where, during process stage 23, thedirection of movement of the lifting mechanism is measured, for example,by making a comparison with previously measured positions of lift of thelifting mechanism. However, it is also possible to use special sensorsfor this purpose.

The determined actual length of the upper steering arm 7 is compared tothe stored nominal length, which is stored for the determined actualposition of lift and for the determined direction of movement of thelifting mechanism (process stage 24). During process stage 25 it isdecided whether the actual length deviates from the stored nominallength. If this is not the case, the process continues with processstage 21. However, if a deviation has occurred, the power drive of theupper steering arm 7, in process stage 26, is controlled so that thelatter assumes the nominal length position.

The upper steering arm 7 is preferably a hydraulically actuated steeringarm. The steering arm comprises a double-acting hydraulic cylinder 27.Thus, it is possible for the length of the upper steering arm 7 to beadjusted via the hydraulic system to any value.

The process stage 25 and the process stage 26, in connecting point 28,can be followed by further process stages which will be explained below.Thereafter, the process is continued by process stage 21.

FIG. 3 shows a flow diagram with process stages referring to the manualsetting of a floating position of the upper steering arm 7. Inconnecting point 28, according to FIG. 2, the process can follow theprocess shown in FIG. 2. In accordance with process stage 29, thequestion is asked as to whether the system has been switched manually toa floating position. The manual switching can be effected by anoperative switching of the operating unit. If such a manual input hasbeen effected, the upper steering arm 7 is released. Thus, depending onthe position of the implement, the length of the upper steering arm 7can be freely set. The process stage 30, for releasing the uppersteering arm 7, can be replaced by further process stages, as will beexplained later. For example, in order to release the upper steering arm7, the hydraulic cylinder 27 can be connected to a hydraulic tank andthus disconnected by a hydraulic pump. Accordingly, a piston rod 31,connected to the coupling hook 9 of the upper steering arm 7, is able tomove freely.

FIG. 4 shows a flow diagram with the process stages for automaticallyreleasing the upper steering arm 7 and thus for automatically setting afloating position of the upper steering arm 7. Again, these processstages can follow in connecting point 28, according to FIG. 2 theprocess stages shown in FIG. 2. The process stages can also follow theprocess stages according to FIG. 3.

Initially, in process stage 32, data is made available and stored inmemory 18 of the control unit. The data indicates in which position oflift of the lifting mechanism a floating position of the upper steeringarm 7 should be set. For this purpose, releasing information is storedfor certain ranges of positions of lift. The releasing information canbe a “yes” information or “no” information for certain ranges ofposition of lift. The actual position of lift of the lifting mechanismis determined in process stage 33. The information is examined inprocess stage 34 to determine whether the actual position of lift, asdetermined, falls within a range of positions of lift for which apositive or negative releasing information has been stored. If apositive releasing information has been stored, the upper steering arm 7is released in process stage 35. The release corresponds to thataccording to FIG. 3 and can contain further process stages. If nopositive releasing information has been stored, the release of the uppersteering arm 7 does not take place and the process continues.

The above-defined process stages for releasing the upper steering armaccording to FIGS. 3 and 4 can be represented by the following processstages according to FIG. 5. The process stages serve to delimit thefloating path of the upper steering arm 7. For this purpose, a nominallower length limit and a nominal upper length limit are provided inprocess stage 36 and stored in memory 18 of the control unit. Thenominal lower length limit and the nominal upper length limit can beaccurately defined or vary, depending on the position of lift. Inprocess stage 37, the actual length is examined to determine whether itis located between the nominal lower length limit and the nominal upperlength limit. If this is the case, the upper steering arm 7 is releasedin accordance with process stage 38. Thus, the upper steering arm 7 canbe set to any length. If the actual length is not located between thenominal lower length limit and the nominal upper length limit, the uppersteering arm 7 is not released. Instead, the power drive of the uppersteering arm 7 is controlled in process stage 39 so that it assumes alength which is located between the nominal lower length limit and thenominal upper length limit. Thereafter, the process is continued.

Before the upper steering arm 7 is released in accordance with theprocess stages according to FIGS. 3, 4 or 5, a system check is conductedin accordance with the process stages shown in the flow diagramaccording to FIG. 6. It is examined whether the upper steering arm 7 canbe released in order to avoid uncontrolled downward pivoting of theimplement, when the implement is lifted off the ground for example.First, in process stage 40, a limit value is made available in thememory 18 of the control unit. The limit value corresponds to the forceacting on the upper steering arm 7. In the case of a hydraulic uppersteering arm 7 with a double-acting hydraulic cylinder 27, it ispossible for a limit value for the pressure in the hydraulic cylinder tobe made available. Thereafter, the actual value is measured in processstage 41. If a hydraulic upper steering arm is used, the actual value isthe pressure in the hydraulic cylinder. In accordance with process stage42, it examines whether the pressure in the hydraulic cylinder is aboveor below the limit value. If the limit value is exceeded, this indicatesthat a high tensile force is acting on the upper steering arm 7.Consequently, if the upper steering arm 7 is released, the implementwould pivot downwards in an uncontrolled way. Therefore, if the limitvalue is exceeded, it is impossible for the upper steering arm 7 to bereleased. However, if the limit value is not reached, the upper steeringarm can be released (process stage 43).

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A process of setting the length of an upper steering arm of anattaching device of a tractor, wherein the attaching device comprisesthe upper steering arm with a power drive provided for length settingpurposes, a length sensor for determining the actual length of the uppersteering arm, two lower steering arms with a lifting mechanism forlifting and lowering the lower steering arms, a lift sensor fordetermining the actual position of lift of the lifting mechanism, aswell as a control unit, said process comprising: providing nominallengths of the upper steering arm in a memory of said control unit, saidnominal lengths are stored in the control unit as a function ofpositions of lift and directions of movement of the lifting mechanism tobe determined; determining the actual length of the upper steering arm;determining the actual position of lift of the lifting mechanism;determining the direction of movement of the lifting mechanism;comparing the actual length with the stored nominal length for thedirection of movement to be determined and for the actual position oflift to be determined; and controlling the power drive for setting thelength of the upper steering arm to the nominal length if the actuallength deviates from the nominal length.
 2. A process according to claim1, further comprising storing in said memory nominal lengths for thedirection of movement of lifting the lifting mechanism for the positionsof lift to be determined in the form of a first characteristic curve andstoring nominal lengths for the direction of movement of lowering thelifting mechanism for the positions of lift to be determined in the formof a second characteristic curve and said first characteristic curvedeviates from the second characteristic curve.
 3. A process according toclaim 2, wherein the first characteristic curve is shaped in such a waythat the speed at which the upper steering arm is set, starting from alowered position of the lifting mechanism, at least along part of thelifting path, to a raised position of the lifting mechanism, is limitedduring the lifting operation.
 4. A process according to claim 1, furthercomprising releasing the upper steering arm so that with respect to itslength said upper steering arm is freely movable when a signal is sentfrom an operating unit to the control unit.
 5. A process according toclaim 4, further comprising storing releasing information in the controlunit so that a floating path should be set at the upper steering arm ifthe position of lift to be determined is within a certain stored rangeof positions of lift, comparing the actual position of lift with therange of stored positions of lift for the releasing information, andreleasing the upper steering arm so that the upper steering arm, withrespect to its length, is freely movable if the actual position of liftis within the range of stored positions of lift for the releasinginformation.
 6. A process according to claim 5, further comprisingstoring a nominal lower length limit and a nominal upper length limit inthe control unit as a function of the positions of lift of the liftingmechanism to be determined, releasing the upper steering arm andcontrolling the power drive so that the upper steering arm, with respectto its length, is freely movable between the nominal lower length limitand the nominal upper length limit stored for the actual position oflift.
 7. A process according to claim 6, further comprising storing alimit value in the control unit and said limit value represents themaximum force which acts on the upper steering arm and at which theupper steering arm can be released for the purpose of achieving afloating path, determining an actual value which represents the forceacting on the upper steering arm, comparing the actual value with thelimit value, and releasing the upper steering arm only if the actualvalue is below the limit value.